This invention relates to separation of hydrogen from a gaseous mixture. More specifically, it relates to the use of a novel solid electrolyte and a catalyst in removing hydrogen from a gaseous mixture containing a component capable of dissociating to yield hydrogen ions.
The Nernst equation provides a mathematical description of such a system, as follows. When two media with different partial pressures, P.sub.1 and P.sub.2, of a particular substance present in both media are separated by a solid electrolyte (ionic conductor) and conducting electrodes attached to both sides of the ionic conductor are connected by an electrical conductor, ions flow through the electrolyte and current flows in the external circuit established by the electrical conductor. An EMF is generated which is related to the partial pressures as follows: ##EQU1## where R is the gas constant, T is absolute temperature, F is the Faraday constant, E.sub.o is the standard oxidation-reduction potential difference, EMF is electromotive force, and n is the number of electrons per molecule of product from the overall cell reaction (a measure of ion flow). If the system described by the above equation behaves non-ideally, the partial pressures must be replaced by fugacities. Another factor which may need to be considered in regard to a particular system is the rate of dissociation to form the ions which pass through the solid electrolyte. This may be a limiting factor to the transfer of ions through the electrolyte. The rate of dissociation can be calculated by means of the equilibrium constant for the dissociation reaction.
A novel solid electrolyte membrane is used in the present invention. We have discovered that a polymer blended membrane may be fabricated by admixing a heteropoly acid or a salt thereof with an organic polymer which is at least partially compatible with said heteropoly acid or salt to form a polymer blended composition of matter which is useful in hydrogen separation. It was totally unexpected that a thin film membrane could be cast from such a blend to provide a membrane which would be highly selective to certain gases and therefore able to act as a proton conductor in a hydrogen separator where molecular hydrogen is converted into protons on one side of the device, transported through the membrane and recombined as molecular hydrogen on the other side. The membrane is also useful in separating gases capable of dissociating into hydrogen ions. For background information relating to the present invention, reference may be made to the book Solid Electrolytes and Their Applications, edited by Subbarao, Plenum Press, 1980.